Updated

Washington is bracing for the clock to strike midnight, with a government shutdown expected if Congress cannot strike a budget deal -- but despite the frenzy, the government might not turn into a pumpkin right away.

Everybody is talking about a midnight deadline, because that is the official time that all discretionary spending (which is the portion that Congress controls) halts as the federal government rolls over from fiscal 2013 to fiscal 2014 on Oct. 1.

That doesn't mean that everything stops immediately, however.

For starters, if there is a shutdown, most federal workers will be asked to come to the office on Tuesday morning to transition to an "orderly" shutdown. They must turn in BlackBerries and cell phones. Systems must be shut down.

In other, words, they just don't switch off the lights.

But there's another way that the government might keep operating past midnight, even if lawmakers have not yet reached a deal.

In March, 2011, the government inched within a couple of hours of a shutdown. To stave it off, they forged an agreement at around 10 p.m. ET. The Senate okayed the package by unanimous consent just before midnight -- however, the House did not approve the package until nearly 12:45 a.m. And the president did not sign the bill until nearly 2:30 p.m. the next day.

But the government stayed open during that time.

How come?

Three reasons:

-- Everyone understood there was and would be funding for the federal government, even if from a clerical standpoint, there wasn't.

-- Built into the pending bill was legislative "grout" -- backfill to cover the time where appropriations lapsed.

-- A key aide to House Speaker John Boehner, Ed Cassidy, had a pre-written email ready to send to the Office of Personnel Management (OPM), the governing body for the federal workforce. So long as Cassidy did not hit "send" on his email, the government remained open.

So, it's possible -- and this is hypothetical -- that the government may not shut down if they are still negotiating late into the night on Monday and early Tuesday morning. There's precedent for that.

Over the weekend, the House passed a measure that would fund the government past Sept. 30 while also delaying ObamaCare. Senate Democrats have vowed to reject it.

But so far, there are no talks and little consideration now of an emergency measure to stave off a shutdown overnight. Senate sources have signaled they would not accept a stopgap bill to fund the government for a few days.